This International standard describes procedures for on-site measurement of crystalline silicon photovoltaic (PV) array characteristics and for extrapolating these data to Standard Test Conditions (STC) or other selected temperatures and irradiance values. Measurements of PV array I-V characteristics under actual on-site conditions and their extrapolation to Acceptance Test Conditions (ATC) can provide (see annex A and QC 001002): - data on power rating - verification of installed array power performance relative to design specifications - detection of possible differences between on-site module characteristics and laboratory or factory measurements - detec